Precision spray coating device



Dec. 27, 1966 M. A. SHRIRO 3,294,058

PRECISION SPRAY COATING DEVICE Filed April 19, 1965 5 Sheets$heet 1 PRESSURE REGULATING VALVE 52 49 W 53 MOTORlZED TO 49 VALVE M BY Mm! Wm;

Dec. 27, 1966 M. A. SHRIRO 3,294,058

PRECISION SPRAY COATING DEVICE Filed April 19, 1965 5 Sheets-Sheet 2 4 I 448 ll H v 446 \T 442 4 444 I -L I L INVENTOR' MORRIS A. SHRIRO BY ynwk Dec. 27, 1966 M. A. SHRIRO PRECISION SPRAY COATING DEvIcE 5 Sheets-Sheet 5 Filed April 19, 1965 INVENTOR, MORRIS A. SHRIRO FIG. 6

MMA

ATTORNEY Dec. 27, 1966 M. A. SHRIRO 3,294,058

PRECISION SPRAY COATING DEVICE Filed April 19, 1965 5 Sheets-Sheet A T TORNE X 5 Sheets-Sheet b ATTORNEY Dec. 27, 1966 M. A SHRIRO PRECISION SPRAY COATING DEVICE Filed April 19, 1965 m l 11 m 1 ms 6 8 m m m m 7 y m z W 6 Z 2 v Q 4 A. 8 6 U WM 3 m 4.. kgwmwfim 1 i it m MW .1 2 u 0 N 3 7 w w m Z w 2 United States Patent C) lC 3,294,058 PRECESEON SPRAY QUATING DEVICE Morris A. Shriro, 88 Sheridan Ave, Mount Vernon, NY. 13476 Filed Apr. 19, 1965, Ser. No. 451,095 24 Claims. (Cl. 118-11) This application is a continuation-in-part of copending application Serial No. 314,581, filed October 1, 1963, now abandoned.

This invention relates to precision liquid coating devices and more particularly to an apparatus capable of depositing a uniform coating on a substrate.

Spray devices have long been employed for dispensing a broad range of materials such as insecticides and coating materials such as automobile finishes. In such applications minor variations in the quantity of material deposited and uniformity of coating are not particularly critical. In many applications the customary permissible tolerance is so large that reliance is usually placed on the visual observation of the operator who varies the procedure to obtain a satisfactory coating. In coating an automobile, for example, a variation of coating thickness from one part to another of as much as 25 percent would not be particularly noticeable. In industrial finishing operations the lacquer or other finishing material is frequently supplied from a fifty-five gallon drum, thereby enabling the operator to use a substantial amount of liquid in adjusting his equipment without any problem. The device of this invention is not intended for such noncritical purposes. As will be explained in greater detail hereinafter, the apparatus of this invention makes practical the use of a small quantity of a coating material, say a total supply of 5 or cc., and permits the application of such material to a substrate with a surprisingly high degree of uniformity and without reliance on the skill of the particular operator. Where the coating material is costly or rare, the capability of operation with small quantities is an important advantage. One application of this invention is in the coating of a portion of an insulator base with a resistance material to form a resistance element. Such elements are employed, for example, in precision otentiometers. As employed herein, the term precision otentiometers is intended to encompass devices having a deviation as small as 0.05% or even 0.01% or better. Deviation is the plus or minus difference between the actual resistance and the straight-line resistance function at any point expressed in percent of the total resistance. It will be appreciated that to attain the uniformity of coating that is necessary to produce a precision potentiometer requires a unique coating device. Of course this is not to say that conventional spray guns cannot be used for this purpose, but experience has shown that when conventional spray guns are employed, an extremely high rejection rate results.

In the manufacture of potentiometer elements, a fluid suspension of the resistance material is employed. This creates a serious problem since considerations of accuracy and control require that the orifices of the spray apparatus be small. Since the orifices are small, the deposition of even a small particle in the orifice will make an appreciable difference in the area of the orifice. Where the rate of delivery of the coating material is dependent on the area of the opening, as in the conventional venturi type gun, this can lead to very erratic behavior.

In the conventional venturi type spray-guns, an air stream is used to aspirate the spray material from a container and then propel particles onto an object to be coated. Variations in the pressure of air, seriously affect the rate at which the spray material is drawn from the container and under these circumstances it is usually necessary to provide elaborate, expensive, and space con- 3,294,058 Patented Dec. 27, 1966 suming devices designed solely to maintain constant pressure which will produce a fairly uniform spray coating. Further, the distance of throw, rate of feed, and force with which the sprayed material strikes the surface to be coated, are all interrelated making control of the coating inadequate for the purposes for which the present invention is intended.

In another conventional spray device, the pressure type, the spray material is forced out of a nozzle, by a piston or air pressure. However, sedimentation of the suspension in the barrel of the device is likely to cause the serious problem of irregular feed rate. This will be particularly apparent when a comparatively long spray time is required by the process or when the solids in suspension are particularly heavy. Metallic silver dispersions, for example, provide a particularly severe problem. This latter type of system also suffers from the same defect as the first mentioned system, namely, that the projecting force applied to particles being sprayed and the feed rate are not independent.

Although the art of spraying is old, as far as is known, prior to this invention no really precise spray device has been available.

It has been found that by removing the interdependence of the two operations, namely, (1) the supplying of the spray material from a container, and (2) the projecting of the spray material, it i possible to produce a precision spray device capable of repetitively reproducing identical continuous spray conditions. The apparatus disclosed hereinafter may advantageously be employed for manufacturing resistance elements, or the like, wherein extremely uniform characteristics are required and where it is important that the elements be succes sively reproduced with uniformity between successive items.

It is, therefore, an important object of this invention to provide a precision spray apparatus for uniformly coating a substrate.

It is another important object of this invention to provide a precision spray-gun wherein the feed of the spray material is divorced from the air pressure needed to project the material.

Another important object of this invention is to provide a precision spray-gun capable of accurately reproducing the same spray on successive attempts.

It is a principal object to provide a spray-gun characterized by a uniform feed of spray material.

Still another important object of this invention is to provide a precision spray-gun which is not subject to variations in operating air-pressure.

A further object is to provide a suspension material feed system having means to prevent the accumulation of sediment therein.

An additional object is to provide an agitator operating cooperatively with the piston of the material feed mechanism.

A further object is to provide independent drive means for the aforementioned agitator.

Still other features and advantages of the invention will, in part, be obvious and, in part, are set forth with particularity as the following description proceeds. The invention itself, however, both as to its organization and method of operation, may best be understood by reference to the following description taken in conjunction with the accompanying drawing.

In the various figures of the drawing like reference characters designate like parts.

In the drawing:

FIG. 1 represents, in elevation partially broken away, one embodiment of the invention utilizing a lead screw feed mechanism.

FIG. 2 represents another embodiment of the invention utilizing a rack and pinion operated spray material feed mechanism.

FIG. 3 represents still another embodiment of the invention utilizing a hydraulically operated spray material feed mechanism.

FIG. 4 shows, partially broken away, another spraygun embodiment.

FIG. 5 shows, in plan, a typical spray deposited coating on a substrate, with a mask member shown partially broken away to expose the substrate.

FIG. 6 shows in elevation, partially broken away, another embodiment of the invention employing a rotating piston.

FIG. 7 is an elevation view, partly schematic, illustrating a preferred embodiment of the invention.

FIG. 8 is an enlarged sectional elevational view illustrating the relationship of the piston, the agitating means and the connective means of the FIG. '7 embodiment.

Referring now to FIG. 1, there is shown a vertical support member 14 mounted on a base 12. Upon one side of support member 14 there is positioned a motor 16, whose operation will be described hereinafter. The shaft of motor 16 has a pulley 18 mounted thereon, which pulley drives belt 20. Belt 20 drives pulley 22, which in turn is connected to gear 24 to drive the gear when motor 16 is operating. It is preferred that a cog type belt and suitable mating pulleys be employed to insure positive drive. Gear 24 is mounted between pillow blocks or journal bearings 26. Gear 28, in mesh with gear 24, is coupled to a high pitch screw 29. The screw is part of a micrometer-type mechanism designated generally as 30. The lead screw portion 29 is threaded into a tapped barrel 31. One end of the screw vis coupled to thimble 33. Gear 28 is likewise fastened to thimble 33. The micrometer-type feed mechanism 30 is aflixed to support 14 by clamp 32 secured to barrel 31. The free end of the lead screw terminates in spindle 34 which engages ram 36. Clamp 40, affixed to upright 14, holds a spray material supply and feed mechanism designated generally as 38, and is designed to allow mechanism 38 to be easily removed for filling and cleaning purposes. Mechanism 38 includes a barrel 42 with a central bore 44 and a piston 36, designed for a very tight sliding fit in the barrel. It is essential that the cylinder frictionally engage the piston so as to prevent it from coasting away from the actuating rod 34. Further, it is essential that means he provided for preventing the entry of atmospheric air at the bottom of the cylinder as a result of aspirating action.

The barrel 42 terminates in a stepped portion 43. Nozzle portion 47 is removably secured to stepped portion 43 by means of a tight fit between the inner diameter of nozzle 47 and the outer diameter of stepped portion 43. The top of nozzle 47 is provided with a very fine orifice 46 through which the spray material is exuded.

Immediately adjacent orifice 46, and axially disposed with respect to the work 60 to be sprayed, there is provided a source of gas 51 under high pressure. The term air as used here is intended to broadly denote a source of compressed gas, be it nitrogen, helium, air or other gas. Suitable means for regulating the air pressure applied to the apparatus are known to the art and accordingly are not described in detail. The air 51 is transported after passing through suitable pressure regulator 52, through tube 53 and is exhausted through orifice 54 which is in close proximity to the spray material exuded through orifice 46. The air stream atomizes the liquid thus exuded from the nozzle into particles 37 which are then carried to the surface 60 to be coated. The velocity of the gas passing through orifice 54 is a function of the orifice area and gas pressure. Since the orifice area is kept constant, the pressure regulator 52 may be adjusted v to provide a gas velocity such that the exuded liquid will be atomized.

The surface 60 may be an insulator and the fluid 37 may be a dispersion of a conductive carbon in a resin binder to form a resistance element.

The operation of the apparatus for the deposit of a pattern such as shown in FIG. 5 is described hereinafter. While the description is particularly concerned with an automatic system, it will be apparent that manual controls, such as conventional electrical switches, may be employed.

As shaft 68 of the timing device rotates, cam 57 closes switch 58 which opens valve 49 to start the flow of air. In sequence, cam 69 closes switch 70 so as to energize motor 76. The article 60 which is to be coated is supported by the shaft of motor 76. After a predetermined time, sufi'icient to enable motor 76 to achieve constant speed, cam 71, also afiixed to shaft 68, closes switch 73 to energize motor 16.

On rotation of the shaft of motor 16, belt 22 imparts a rotary motion to gear 24 which in turn causes micrometer-feed mechanism 30 to force spindle 34 into engagement with piston 36. As piston 36 traverses up through the bore of cylinder 38, any material 37 that has been placed in the bore 44, will be forced out of orifice 46 and into the path of the air leaving orifice 54.

At a predetermined time after the start of the spray operation, solenoid 72 is energized through the action of cam 75 in closing switch 77. Solenoid 72 is coupled to shutter 74 causing it to be withdrawn from the path of the spray of particles 37 permitting them to be deposited on substrate 60. After a predetermined spray period, which may be varied by substitution of a suitably shaped cam, switch 77 opens thus deenergizing solenoid 72. In turn, the shutter 74 returns to its rest position so as to block the path of the spray. In sequence, the motor 16 is deenergized and air valve 49 is closed.

The pattern deposited by the spray gun is rather small, occupying, for example, an area covered by a circle having a diameter of /2 at a distance of 1 /2". The taper of coating 501 shown in FIG. 5 is readily obtained by masking the substrate 502 to be covered with a suitably shaped cutout mask 61.

Where it is desired to coat a linear or straight line pattern, it has been found convenient to mount stand 12 on a slide mechanism and have it traverse the article which is maintained in fixed position. The shutter 74 may be controlled by an actuating means having its actuating point related to the position of the article to be coated. This actuating means may comprise a cam member arranged to contact a conventional limit switch. The cam may extend from a jig supporting article 60 in a fixed relation to the portion of the article to be coated and the limit switch may be mounted on the stand 12 so as to be actuated by the cam when the spray gun is at the proper position.

After gear 28 has advanced to the limit of its travel, limit switch 87 is automatically actuated to deenergize motor 16. It is obvious that switch 56 may be manually actuated to deenergize the system if desired. Thus, there has been provided a means for supplying spray material to a spray-gun at a constant rate which is completely independent of the air-pressure being used to deposit the material. Conventional motor reversing means are employed to return the spindle 34 to the starting position.

Referring now to FIG. 2, there is shown a second embodiment of the invention wherein the lead screw feed mechanism 30 of FIG. 1 has been replaced with a rack and pinion type feed mechanism designated 230. In this embodiment, rack 228 and gear 224 are meshed in a manner similar to the feed mechanism of FIG. 1. A mechanical linkage 234, which may be a simple shaft, engages piston 236 of cylinder 238. As the rack 228 advances, fluid to be sprayed is forced from orifice 246.

Switches 256 and 257 provide means to control motor 216 suitably geared to gear 224, in accordance with the position of the rack. Switch 256 may be manually or automatically actuated to initiate the cycle. Switch 257 may serve as a limit switch to stop the operation when the desired distance is traversed by the piston 236.

Referring now to FIG. 3, there is disclosed still another embodiment of the invention wherein a hydraulic feed system is used. In this embodiment, constant speed motor 316 actuates hydraulic pump 317 which, in turn, forces hydraulic fluid into cylinder 319 to displace piston 339. A mechanical linkage 334 transfers the motion of piston 330 to piston 338 thereby forcing spray material out of the orifice 346 into the path of the air stream.

Switch means 356 is provided to control motor 316. Either automatic or manual controls for this purpose may be employed.

In FIG. 4, another embodiment of this invention is disclosed. Member 410 is a cylinder provided with a stepped inner diameter. In the larger diameter portion 413 of cylinder 410, there is fitted an internally threaded polytetrafluorethylene plug 412. (In place of the polytetrafluorethylene, other slippery resilient plastics may be employed.) The plug is force fit into cylinder portion 413 and is secured therein against movement by set screws 415. Threaded piston 414 provides a close fit with sleeve 412. This feature is important as it prevents the entrance of air into the cylinder. One end of piston 414 is coupled to a gear 416. Gear 416 meshes with pinion 418. Pinion 418 is rotatably supported in journal bearings 429 and 422. A shaft 424, extending from pinion 418, is coupled to motor 426 by gear train 428. As piston 414 is rotated, it advances into the chamber, which is normally filled with fluid. Fluid displaced by the piston is exuded from the orifice. It should be noted that by taking advantage of the displacement concept the need for a closely fitted piston is avoided. This simplifies manufacturing of the device and extends the useful life of the device. In this apparatus there is no danger of binding the piston in the cylinder.

Filling of the cylinder is accomplished by removing nozzle 440, withdrawing the piston 414 to the lower portion of the cylinder, and introducing the fluid to be sprayed into the upper portion of the cylinder.

Orifice assembly 440 couples to reduced diameter threaded portion 430 of cylinder 410. The orifice assembly includes an internally threaded coupling member 442, which mates with member 430, and which threads downwardly onto member 430 so as to seat O-ring 444 in the bore of member 430. After member 442 is properly positioned, collar 446 is locked onto threaded portion 448 by means of locking screw 450. Tool 452 is then inserted in an opening in member 446, and the orifice assembly 440, together with the cylinder assembly, is adjusted vertically to raise the orifice to the desired elevation.

Locking screw 460 is then loosened and barrel 462 is rotated until the air jet orifice 464 is properly oriented with respect to the tube 466 of nozzle assembly 440. The correct position is readily determined by the operator by spraying a surface and noting the pattern produced. When properly oriented a perfectly circular pattern results. Barrel 462 clamps into a supporting member by means of a spring loaded ball detent means 470. A conventional coupling is provided between barrel 462 and the air supply hose 472.

In FIG. 6 there is disclosed an embodiment of the invention which utilizes fixed O-ring seals 602 to provide a positive seal against entry of atmospheric air at the bottom of the cylinder as a result of aspiration of the fluid. In contrast to the device of FIG. 1, this embodiment will tolerate a loose fit between piston and cylinder, thus permitting significant savings in manufacturing cost and longer life. The O-rings provide sufficient frictional engagement so as to prevent coasting of the piston.

There is normally a tendency for the piston to advance stepwise despite the screw feed because of the seizing action of the O-rings which release only after suflicient pressure is built up by the screw. As a result, the fluid is dispensed in spurts. To overcome this defect, it has been found necessary to couple the leadscrew spindle 34 and the piston 36 so that they rotate together thereby imparting a sliding action between the piston 36' and O-rings 602. A simple key arrangement 604, as shown, has proved adequate for providing the desired combined rotation. Other elements in FIG. 6 having primed reference characters are similar in function to like elements in FIG. 1 but have slight structural changes to suit the O-ring and key arrangements.

The preferred embodiment of the present invention is disclosed in FIG. 7 and FIG. 8. A micrometer lead screw 760 is driven, as in the previous embodiments, by motor 16, a belt and pulley arrangement comprised of pulleys 18 and 22 having belt 20 trained thereabout, and a gear train 752. Gear 764 is secured to thimble 766 which is coupled to the lead screw by means of barrel 7%. Pinion gear 710 is suitably journaled in and supported by a bracket and has pulley 22 mounted on one end thereof.

As may be seen in FIG. 7, the longitudinal axis of pinion gear 710 and lead screw 7% are substantially parallel. An improved spray material and feed mechanism assembly, generally designated as 712, is coaxially and rotatably secured to the upper end of lead screw 700 by means of a cup-shaped externally threaded member 714 and a nut 716. Shaft 718 which extends outwardly of the bottom end of assembly 712 and is journaled in member 714 is provided with a pulley 729 adapted to be driven by motor 722 through belt 724. Gear 726, secured to the piston of assembly 712, is in meshing engagement with pinion gear 728 which is an extension of pinion gear 710. It will be appreciated then that the lead screw and the piston are both driven by the same motor. However, shaft 718 is arranged to be rotated independently of both elements, as will now be explained in conjunction with FIG. 8.

Piston 730 is hollow and shaft 718 is arranged coaxially and concentrically therein. Bearings 732 rotatably supports the lower end of shaft 718 in cup-shaped member 714. Shaft 718 is also rotatably su ported by upper and lower bearings 734 and 736, respectively, disposed within central opening 738 of piston 73th. Spacer 740 is provided between pulley 729 and bearing 736 and retainer 742 is provided on the bottom end of the piston to capture bearing 736. Upper and lower stufiing boxes 744 and 746, respectively, are also disposed in the central opening of the piston just above each of the bearings 734 and 736. Retainer 748 secures the upper stuffing box and bearing in place.

Agitator blade 750 is threadably secured to the upper end of rotatable shaft 718 and together with the piston is enclosed by cylinder 752 having an orificed member 754 secured to the upper end thereof. O-rings 754 are disposed between the inside diameter of cylinder 752 and the outside diameter of piston 730. The improved spray material and feed mechanism assembly, the lead screw assembly, the gear train and motors, are mounted to a support bracket in a manner similar to that shown in the previous embodiments. The FIG. 7 embodiment also includes such other switching, valving, regulating and worksupporting mechanism, as described in conjunction with the previous embodiments.

In addition to maintaining the supplying of the spray material independent of the projecting of the spray material, the FIG. 7 embodiment provides agitation of liquid to be sprayed. The concentrically and coaxially mounted agitator blade is disposed directly in the liquid and is rotated by a separate motor. Thus, even while the apparatus is not operating in the spray mode, the liquid may still be agitated. Of course, the liquid could be agitated concurrently with the spraying process.

As a further advantage of the disclosed system, the rate of agitation may readily be varied in keeping with the viscosity of the liquid, the periods of use and nonuse of the equipment, or the rate at which sedimentation of the suspension in the barrel will occur. The sedimentation problem is particularly apparent when a comparatively long spray time is required by the process or when the solids in suspension are particularly heavy as, for instance, when the suspended conductive material is silver. In this regard, it should be noted that the inclusion of stuffing boxes in the piston central chamber prevents the material being sprayed from flowing downward into the bearings and contaminating them.

The third, external bearing, disposed between the adjacent ends of the lead screw and the agitator shaft rotatably couples the two members so that only a vertical movement is applied to the piston by the lead screw. The second, upper set of gears driven by the same motor as the lower set provides rotary movement to the piston which is free to move within the O-rings.

There has been disclosed heretofore the best embodiments of the invention presently contemplated and it is to be understood that various changes and modifications may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. A precision spray device comprising:

a two-ended barrel for receiving a coating liquid;

a piston, having a longitudinal axis, slidably positioned in said barrel with one end extending therefrom; gear actuated means for moving said piston along said barrel;

a controlled actuating means to drive said gear actuated means;

orifice means partially closing the other end of said barrel;

an air orifice situated proximate to the end of the said orifice means; and

regulator means for controlling the velocity of air from said air orifice to remove liquid from said orifice means at the rate at which it is exuded from said orifice means by the operation of said piston.

2. The device in accordance with claim 1 including means positioned in said barrel intermediate said orifice means and the internally disposed end of said piston for agitating the coating liquid.

3. The device in accordance with claim 2 including means to actuate said agitating means independently of the movement of said piston.

4. A precision spraying apparatus comprising:

a hollow cylinder for receiving a liquid to be sprayed;

:a piston fitting closely to the inner wall of said cylinder;

driving means for moving said piston;

.a restricted orifice partially enclosing one end of said cylinder;

:a source of gaseous fluid arranged to be projected in a confined stream at substantially right angles to said orifice; and

regulator means for controlling said stream in synchronization with the operation of said driving means for moving said piston within said cylinder to aspirate the liquid from said orifice at the rate at which it is exuded.

5. The apparatus in accordance with claim 4 including means positioned in said cylinder intermediate said restricted orifice and the end of said piston proximate said restricted orifice for agitating the liquid to be sprayed.

6. The apparatus in accordance with claim 5 including means to actuate said agitating means independently of the movement of said piston.

7. A precision liquid dispensing apparatus comprismg:

a bore adapted to receive a liquid to be sprayed;

a piston adapted to slide in said bore in close fitting relationship;

a threaded portion connected to said piston;

a resilient, slippery, synthetic resin sleeve having an internal thread receiving said threaded portion so that the threaded portion rotates therein;

means securing said resilient sleeve in said bore so as to provide an airtight seal between the interior of said bore and the outside atmosphere;

an orifice member adapted to partially close one end of said bore; and

means providing a jet of gas proximate the orifice to aspirate fluid exuded by the action of said piston.

8. The apparatus of claim 7 wherein said orifice member comprises:

a cylinder adapted to slide in a close fit with said bore;

an O-ring seal positioned between said cylinder and said bore; and

threaded means for adjustably securing said orifice member in a desired position.

9. The apparatus in accordance with claim 7 including means positioned in said bore intermediate with said orifice member and the end of said piston proximate said orifice member for agitating the liquid to be sprayed.

10. The apparatus in accordance with claim 9 including means to actuate said agitating means independently of the movement of said piston.

11. An apparatus for precision coating of a workpiece in a predetermined pattern comprising:

a cylindrical chamber for receiving a liquid to be deposited on said workpiece;

a piston engaging the walls of the chamber in a close sliding fit;

an orifice member partially enclosing one end of said chamber and provided with an orifice communicating with the interior of said chamber;

means to move said piston at a constant rate so as to exude liquid contained in said chamber through said orifice at a constant rate;

a valve, for turning on and off gas from an external source in series with means for regulating the flow of said gas and means directing said gas across said orifice so as to provide removal of said exuded liquid at the rate of extrusion to form a -liquid spray;

means for supporting said workpiece to be coated;

means for moving said workpiece and said spray relative to each other;

removable shutter means adapted to be interposed in the path of said spray;

means for positioning said shutter relative to the path of said spray;

a plurality of switches; and

means to sequentially operate said plurality of switches, wherein a first of said switches is arranged to control said valve, a second of said switches is arranged to control said means for moving said piston, a third of said switches is arranged to control said means for moving said workpiece and said spray relative to each other, and a fourth of said switches is arranged to control said means for positioning said shutter relative to the pat-h of said spray.

12. The apparatus of claim 11 wherein said means to sequentially operate said switches includes a timing motor and a series of cams driven by said timing motor.

13. The apparatus in accordance with claim 11 including [means positioned in said chamber intermediate the orifice of said orifice member and the end of said piston proximate the orifice for agitating the liquid to be deposited.

14. The apparatus in accordance with claim 13 including means to actuate said agitating means independently of the movement of said piston.

15. A precision liquid spraying apparatus comprising:

a container, having an inner wall, for receiving liquid to be sprayed;

a member fitted to said container having an orifice communicating with the interior of said container;

an internally threaded slippery synthetic resin sleeve having an internally threaded bore communicating with the interior of said container, a threaded piston member rotatably mounted in said sleeve and spaced from said inner Wall, said threaded sleeve being fitted to said container in an airtight connection; means to rotate said threaded piston member; and means to provide a jet of gas proximate the orifice to aspirate fluid exuded by action of said piston.

16. The apparatus in accordance with claim 15 including means positioned in said container intermediate said orifice and the end of said piston proximate said orifice for agitating the liquid to be sprayed.

17. The apparatus in accordance with claim 16 including means to actuate said agitating means independently of the movement of said piston.

18. An apparatus for precision coating of a workpiece in a predetermined pattern comprising:

a chamber, defined by a wall, for receiving a liquid to be deposited on said workpiece;

a slippery synthetic resin sleeve, joined to said chamber wall in an airtight connection, having an internally threaded bore communicating with said chamber;

a threaded piston rotatably supported in said sleeve extending into said chamber in spaced relationship to said chamber wall;

an orifice member fixed to said wall having an orifice in communication with said chamber;

means to rotate and advance said piston into said chamber at a constant rate so as to exude liquid contained in said chamber through said orifice member at a constant rate;

a valve, for turning on and off gas from an external source, in series with means for regulating the flow of said gas and means directing said gas across said orifice so as to provide removal of said exuded liquid at the rate of extrusion to form a liquid spray;

means for supporting said workpiece to be coated;

means for moving said workpiece and said spray relative to each other;

removable shutter means adapted to be interposed in the path of said spray;

means for positioning said shutter relative to the path of said spray;

a plurality of switches; and

means to sequentially operate said plurality of switches, wherein a first of said switches is arranged to control said valve, a second of said switches is arranged to control said means for moving said piston, a third of said switches is arranged to control said means for moving said workpiece and said spray relative to each other, and a fourth of said switches is arranged to control said means lit) for positioning said shutter relative to the path of said spray.

19. The apparatus of claim 18 wherein said means to sequentially operate said switches includes a timing motor and a series of cams driven by said timing motor.

20. The apparatus in accordance with claim 18 including means positioned in said chamber intermediate said orifice and the end of said piston extending into said chamber for agitating the liquid to be deposited.

21. The apparatus in accordance with claim 20 including means to actuate said agitating means independently of the movement of said piston.

22. A precision spray device comprising:

a two-ended barrel for receiving a coating liquid;

a piston, having a longitudinal axis, slidably positioned in said barrel with one end extending therefrom;

a gear actuated means adapted to concurrently rotate said piston about its longitudinal axis and axially move it with respect to the longitudinal axis;

a controlled actuating means arranged to drive said gear actuated means;

an orifice means partially closing the other end of said barrel;

an air orifice situated proximate to the end of said orifice means; and

a regulator means for controlling the velocity of air from said air orifice to move liquid from the said orifice means at the rate at which it is exuded from said orifice means by the operation of said piston.

23. The device in accordance with claim 22 including means positioned in said barrel intermediate said orifice means and the internally disposed end of said piston for agitating the coating liquid.

24. The device in accordance with claim 23 including means to actuate said agitating means independently of the movement of said piston.

References Cited by the Examiner UNITED STATES PATENTS 1,041,524 10/ 1912 Snyder et al. 1,303,987 5/1919 Sturcke. 2,139,824 12/ 1938 Higgins. 2,160,981 6/1939 OBrien. 2,550,404 4/ 1951 Chasan et al. 2,763,233 9/1956 Hartley et al. 2,906,300 9/ 1959 Becker.

' 2,906,513 9/1959 Tabor.

2,946,486 7/ 1960 Gilmount.

MORRIS KAPLAN, Primary Examiner. 

15. A PRECISION LIQUID SPRAYING APPARATUS COMPRISING A CONTAINER, HAVING AN INNER WALL, FOR RECEIVING LIQUID TO BE SPRAYED; A MEMBER FITTED TO SAID CONTAINER HAVING AN ORIFICE COMMUNICATING WITH THE INTERIOR OF SAID CONTAINER; AN INTERNALLY THREADED SLIPPERY SYNTHETIC RESIN SLEEVE HAVING AN INTERNALLY THREADED BORE COMMUNICATING WITH THE INTERIOR OF SAID CONTAINER, A THREADED PISTON MEMBER ROTATABLY MOUNTED IN SAID SLEEVE AND SPACED FROM SAID INNER WALL, SAID THREADED SLEEVE BEING FITTED TO SAID CONTAINER IN AN AIRTIGHT CONNECTION; MEANS TO ROTATE SAID THREADED POSTION MEMBER; AND MEANS TO PROVIDE A JET OF GAS PROXIMATE THE ORIFICE TO ASPIRATE FLUID EXUDED BY ACTION OF SAID PISTON. 